1. Field of the Invention
The present invention relates to an electronic exchange system, wherein it is easy to alter the functions assigned to the keys of a terminal, and also to a method of controlling such an electronic exchange system.
2. Description of the Related Art
Various types of electronic exchanges are used in telephone networks. Among them is a private branch exchange (hereinafter referred to as "PBX"). The PBX comprises a microcomputer. It can perform many functions at high efficiency, owing to the application of software to the microcomputer. Hence, the PBX not only can perform switching of telephone lines, but also can provide other various services.
The terminals connected to the PBX, such as extension telephones and attendants, also each have a microcomputer can perform various functions, and are highly intelligent. For example, an attendant comprises a microcomputer. It further comprises a handset, a response switch, extension switches, indicator lamps (e.g., LEDs), and a buzzer. The extension switches are to be coupled to extension telephone lines. The indicator lamps are provided for the switches (i.e., the response switch and the extension switches), respectively.
In use, the attendant is connected to the PBX. When the PBX receives a call through an external telephone line (hereinafter referred to as "office line"), it supplies a ringing signal to the attendant. In response to the ringing signal, the buzzer incorporated in the attendant generates an alarm. Hearing this alarm, the human operator at the attendant takes the handset and pushes the response switch. When the response switch is thus pushed, the attendant generates a signal. In response to this signal, the PBX connects the office line to the attendant. As a result, the operator and the caller on the other side of the office line can talk with each other. The operator asks whom the caller wants to talk to.
Upon hearing whom the caller wishes to talked to, the operator checks whether the indicator lamp is on or off which is assigned to the extension telephone of the person being called.
If the indicator lamp is off, indicating that the extension telephone is not occupied, the operator pushes the extension switch. Then, the PBX sets the office line into a "suspended state," and supplies a ringing signal to the extension telephone through the attendant and the extension telephone line so that the extension telephone rings. Then, the receiver of the extension telephone is taken off the cradle. The operator asks the user of the extension telephone whether or not the user desires to receive the call. If the user says he or she will receive the call, the operator performs a transfer operation. The PBX connects the extension telephone to the attendant, enabling the operator to speak with the caller. The operator tells the called person that the caller wants to talk to him or her. When the operator hears that the called party wants to speak to the caller, then he or she operates the attendant, thereby releasing the office line from the suspended state and connecting it to the extension telephone line. As a result, the caller and the called party can talk with each other.
As has been described, the attendant has a number of key switches assigned to respective specific functions. These functions are performed by operating the key switches, under the control of the software applied to the microcomputer incorporated in the PBX. In other words, the functions to which the key switches are assigned are controlled by the PBX. When the operator pushes one of the key switches, for example, the extension key which is assigned to the connection of the office line to the extension telephone line A, the attendant generates a signal representing the code allotted to this key switch. The code signal is transmitted to the PBX.
It should be noted that the PBX further comprises an I/O port and a memory. The I/O port is connected to the attendant. The memory stores key-assign data which is a key-data table showing the codes of the key switches, the functions to which the key switches are assigned, and the logical numbers of the buzzer and indicator lamps of the attendant.
Hence, when the code signal representing the code, which is allotted to the extension switch the operator has pushed, is transmitted to the microcomputer of the PBX through the I/O port, the PBX supplies the attendant with the data item representing the logical number of the indicator lamp provided for the pushed extension switch. In the attendant, the indicator lamp identified by this data item is turned on.
The memory incorporated in the PBX has memory areas, which includes a key-assign data area, an exchange-control program area, a fixed data area, and a work area. The key-assign data, described above, is stored in the key-assign data area.
As is evident from the above, both the attendant and the PBX are controlled in accordance with the software. Therefore, the key switches of the attendant can be assigned to various functions in any arbitrary way, and these functions are performed by operating the key switches under the control of the PBX.
Generally, in an electronic exchange system comprising an electronic exchange and an intelligent terminals (e.g., an attendant), when any one of the key switches of the terminal is pushed, the terminal generates a signal representing the code of the pushed key switch and supplies this code signal to the telephone exchange. In response to the code signal, the telephone exchange performs the function to which the pushed switch is assigned, or telephone exchanging, in accordance with the code signal. To enable the telephone exchange to perform not only the telephone exchanging but also the function to which any pushed switch is assigned, both the terminal and the electronic exchange identify any switch key of the terminal that has been pushed.
With the conventional electronic exchange system, it is indeed possible to assign the key switches of the terminal to various function arbitrarily. However, once the key switches have been assigned to specific functions, respectively, by the manufacturer of the system, it is no longer possible for the user to alter the key assignment unless the user changes the programs stored in the memories of both the terminal and the electronic exchange. Usually it is very difficult for the user to change these programs. The flexibility of software control is not completely utilized in the conventional electronic exchange systems.